1. Field
The following description relates to a lens having a structure for precisely measuring decenter, a light scanning unit, and an electrophotography type image forming apparatus.
2. Description of the Related Art
An electrophotography type image forming apparatus, such as a laser printer, a digital copying machine, or a multi-functional printer (MFP), forms an electrostatic latent image by scanning a light to a photosensitive body via a light scanning unit. The formed electrostatic latent image is developed to a developed image by using a developing agent, such as toner, and the developed image is transferred onto a printing medium.
A light scanning unit is a device for scanning a light emitted by a light source to a designated region, includes a light deflector for scanning a light beam emitted by a light source to a photosensitive body, and includes an optical element (lens) for refracting a light beam emitted by a light source and forming an image therefrom. Optical elements of a light scanning unit includes a collimator lens for collimating a light beam emitted by a light source, a cylindrical lens for focusing a light beam onto a reflective surface of a light deflector, a synchronization detecting lens for detecting synchronization of light beams scanned by a light deflector, and a scanning lens for forming an image on a photosensitive body by using light beam scanned by a light deflector.
Optical elements (lenses) of such a light scanning unit are generally injection-molded. However, due to errors of a mold for injection-molding or various conditions during an injection-molding process, there may be errors in a shape of a lens.
Recently, sizes of lenses have decreased along with the miniaturization of light scanning units, and thus, decenter requirements for lenses are stricter than ever. However, there is no method of precisely measuring interfacial decenter and no method of reducing interfacial decenter.